Rick's Free Auto Repair Advice

High mileage oil and oil filters

What’s the deal with high mileage oil and high mileage oil filters

People always ask me if they should buy high mileage oil. Here’s my take on it.

This article is just one in a series. If you’d like to know more about oil click on the links below.

Choosing the right motor oil

Chrysler’s 3.5-liter engine has oil sludge issues

High mileage oil and oil filters

Oil Viscosity Warning

Synthetic Oil Facts and Myths

Synthetic oil versus conventional oil

What motor oil to use

What oil brand is best

What oil should you use

When to change oil

Best Oil filter

Look around the oil section and you’ll find several companies now offering oil and oil filters specifically designed for high mileage vehicles. You never needed high mileage oil or special filters before, so what makes you think you need it now? Plus, what’s in that oil and those filters that makes them suitable for high mileage vehicles?Fram-HM-w-text


All engines (even new ones) have blow-by. That’s the combustion gas that squeezes past the piston rings and into the crankcase. But high mileage engines have more cylinder and ring wear and thus more blow-by gasses. That’s why oil in high mileage engines turns black much faster than the same oil in a new engine. As your engine wear, you’re literally blowing trash into the crankcase. It’s the oil’s job to take out the trash and the additives help it do its job.

Oil is made up of 25% additives. Those additives contain anti-corrosion chemicals, anti-foaming agents, anti-wear compounds (mostly zinc), and acid neutralizers. High mileage oil has a higher percentage of anti-corrosion, anti-wear, and acid neutralizers than traditional oil. Older engines need that extra protection because they wear out the additives faster. In addition to those additives, high mileage oils also contain seal conditioners. Nitrile seals get brittle and crack as they age and heat takes its toll. Seal conditioners soften the Nitrile seals and make them more pliable. That means fewer leaks from seals.

If you don’t feel like spending the extra money on each quart of high mileage oil, consider this special filter from Fram. Their HM (high mileage) filter contains a cartridge filled with additive gel. The gel sits inside the core tube of the filter and slowly melts as hot oil flows over it. The end result is additive replenishment.


© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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